Freshwater Mussels of the Velika Morava River

Jelena Tomović1, Katarina Zorić1, Margareta Kračun1, Vanja Marković1, Božica Vasiljević1, Vladica Simić2 and Momir Paunović1

 

 

1 University of Belgrade, Institute for Biological Research "Siniša Stanković", Despota Stefana 142, Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 University of Kragujevac, Institute of Biology and Ecology, Faculty of Science, Radoja Domanovića 12, Kragujevac, Serbia

 

Abstract

The aim of this paper is to present the records and relative abundance of freshwater mussels (order Unionoida) along the Velika Morava River. The objective is to contribute to the general knowledge about the distribution of the species. This information is necessary to design more effective assessment of ecological status, as well as to identify the level of endangerment and to set up a prioritisation in protection on the national level. During the investigation five species of mussels were recorded. The most abundant and frequent species was found to be Chinese Pond mussel Sinanodonta woodiana (Lea, 1834), followed by Unio crassus, Philipson, 1788. The records of abundant population of U. crassus is of special interest as the species is assessed as endangered at the European and national level.

Keywords: Unionoida, Velika Morava, community structure

 

Introduction

Freshwater mussels (order Unionoida) are an important component of freshwater ecosystems, especially in large lowland rivers (Csanyi, 2002; Paunović et al., 2007a, 2008; Graf et al., 2008; Tomović et al., 2010). They play a significant role in functionality of ecosystems and could be effectively used as typological parameters and essential organisms in assessment of ecological status of water bodies, as described in EU Water Framework Directive (WFD 2000). Freshwater mussels represent one of the most severely endangered groups of animals due to habitat destruction, introduction of nonnative species, and loss of host fishes, which their larvae (glochidia) are obligate parasites on. Thus knowledge on the distribution of freshwater mussels could contribute to more accurate assessment of the ecological status, as well as design of protection and restoration measures such as habitat restoration or restocking of native populations.

Freshwater mussels of the Velika Morava Basin have not been investigated in a satisfactory way. This order of molluscs of the basin has been studied only as part of macroinvertebrate communities (Marković et al., 2011), or research covering a wider area (Tomović et al., 2010).

Study area

The Velika Morava River originates from the West and the South Morava Rivers. It is 175 km long. With a catchment area of 38.000 km² and mean annual flow of 230 m³ s-1 (gauge station Ljubičevo, near the mouth of the Danube - Annual Water Quality Report 1999-2008), the Velika Morava is one of the major tributaries of the Danube. Over 95% of the basin is located on the territory of the Republic Serbia.

The area is densely populated and the river is under the influence of various pollution (organic, nutrient, as well as other substances originating from industry), hydromorphological pressures (cutting of the meanders, shortening, channelling, gravel and sand extraction).

Material and Methods

During the 2010-2011 macroinvertebrate survey of the Velika Morava River special attention has been placed on collecting data on the distribution of freshwater mussels (order Unionoida).

Benthic samples were collected by benthic hand nets and free diving at five sampling points (Table 1, Figure 1).

 

tab1
Table 1: Sampling sites on the Velika Morava River

 

1
Figure 1: Sampling sites along the Velika Morava

 

The coordinates of the sampling points were measured by GPS ("Garmin Etrex") and charted by using ArcView software (map 1:300,000, system WGS_1984).

Relative abundance was evaluated according to scale presented in Table 2.

 

tab2
Table 2: Relative abundance scale

 

Result and Discussion

During the investigation five species of freshwater mussels (order Unionoida) have been detected (Table 3, Figures 2-6).

The most diversified mussel fauna was observed on the Varvarin and Markovac sites (4 species). On the Bargdan site three species were recorded, while on the Ćuprija site, two species were detected. No mussels were recorded on the Ljubičevo site during the investigation period.

The spatial pattern in species richness could be explained by the influence of pollution, but also by means of habitat richness. Localities Varvarin and Markovac are assessed as less influenced sites according to macroinvertebrate fauna (Marković et al., 2011). At the same time, those sites, together with the Bagrdan site, are characterised by larger amounts of different microhabitats in comparison with the rest of the sites.

The absence of mussels on the Ljubičevo site could be explained by high level of organic pollution (Vasiljević, 2010; Marković et al., 2011) and less diversified habitat. Namely, on the Ljubičevo site the bottom is characterised by clay and artificial stones, which does not provide the conditions for the development of a mussel community.

The most frequent and abundant species according to the data collected during 2010-2011 was found to be a non-indigenous mussel S. woodiana (Chinese Pond Mussel).

Dense population of Thick Shelled River Mussel U. crassus was recorded on the Varvarin, Ćuprija and Markovac sites. According to the BAES database (Simić et al., 2006), as well as our previous investigations (Tomović et al., 2010), the species was not recorded at the Velika Morava River.

U. crassus is of special interest as endangered taxa - assessed as an endangered species according to IUCN classification (Van Damm, 2011). Further, Thick Shelled River Mussel is included in the European Union list of species of special community interest (92/43/EEC), but also covered by Serbian national regulative (Official Gazette of RS 5/2010, listed in Annex 1 – strictly protected species).

It should be underlined that during our investigations the Painter's Mussel Unio pictorum (Linnaeus, 1758) was not detected. U. pictorum is a species that is frequent in large rivers in the region (Csanyi, 2002; Paunović et al., 2007a, 2008; Graf et al., 2008; Tomović et al., 2010). The absence of this species could be explained by high organic and nutrient pollution of the river (Vasiljević, 2010). Thus, the general water quality of the Velika Morava River could be assessed as moderate to poor (class III-IV) based on the results of the national water quality monitoring for period 1999-2008 (Annual Water Quality Report, 1999-2008). The same evaluation was provided by Marković et al. (2011) based on macroinvertebrate communities (III-IV class based on selected metrics). The Painter's Mussel was not recorded during the 2007 survey of the Velika Morava (Tomović et al., 2010) and was not reported for this river in BAES database (Simić et al., 2006). According to Van Damme (2011), based on IUCN classification, U. pictorum has been assessed as Least Concern, since it has a wide distribution and is tolerant to stress conditions. From the other side, the species was found to be sensitive to hydromorphological modification and competition with exotic species (Van Damme, 2011) and biodegradeable pollution (Mouthon, 1996), both being assessed as considerable stressors at the Velika Morava River (SCG ICPDR National Report 2004).